The present invention relates to a fire control system for guns installed on a vehicle and having a stabilized sighting mechanism and a stabilized gun or gun platform, a range finder coupled with the sighting mechanism and a fire control computer for calculating the lead angle and the angle of elevation.
In modern tank fire control systems, stabilization systems are generally employed for the sighting mechanisms and the weapons systems in order to permit aiming and firing during travel of the vehicle. Fire control computers in conjunction with range finders and additional sensors for internal and external ballistic parameters calculate the correction angle for azimuth and elevation. Such an arrangement is disclosed in U.S. Pat. No. 3,575,085.
These fire control computers are usually constituted by electromechanical calculators, electronic analog computers, digital computers or hybrid computers. In order to limit costs, they often are constructed to utilize approximations of certain of the relationships involved in the computations.
Fire control systems of this type already provide an advantageous increase in fighting efficiency. Observation during travel is possible. Firing on stationary targets is effected during an abbreviated firing stop.
In order to fire while traveling and/or on moving targets, it is generally known that, due to the finite flight time of the projectile and the relative movement of the target, lead angles must be considered. These lead angles are usually formed only for lateral, or azimuthal movement, and in some fire control systems additionally also for elevational movement, from the product of the flight time of the projectile, calculated by the fire control computer, and the rated values or the actual values of the angular tracking velocity.
Since the gunner cannot follow the target with his range finder in a constant movement, but rather the crosshair more or less oscillates around the target, the angular velocity indication oscillates correspondingly and the lead angle indication is correspondingly falsified.
Filters with appropriate time constants, or sample and hold or similar memory circuits are used for smoothing. Such filters are employed in the prior art for various purposes unrelated to weapons systems.
Linear filters have the drawback that, due to their required large time constants, the moment of firing is unduly delayed. The storing processes then furnish wrong lead values if, after the moment of sampling, the lead conditions change, as is the case, for example, when traveling around a curve.